Induced pluripotent stem cells (iPS cells) can be prepared by introduction of nuclear reprogramming factors to somatic cells (K. Takahashi and S. Yamanaka, Cell 126 (4), p663, 2006; WO2007/069666). The iPS cells are usually established and cultured using as feeder cells mouse embryonic fibroblasts (MEFs) whose growth was inactivated by mitomycin C or g-ray irradiation. However, cells derived from a different species are used, so there is a possibility that the obtained iPS cells may have an unknown virus or pathogen. Therefore, in some cases, usage of iPS cells established and cultured by a conventional method is not suitable for human therapy. It has been reported that sialic acid which is not produced in human cells was detected on the surface of human embryonic stem cells (ES cells) cultured using MEFs as feeder cells (Martin, M J. et al. Nat. Med. 11, p228, 2005).
It has been reported, so far, that self-replication of human ES cells was maintained by culture using as feeder cells human fibroblasts derived from neonatal foreskin or fibroblast-like cells derived from ES cells (Richards, S. et al. Nat Biotechnol. 20, p933, 2002; Park, J H. et al. Bio. Reprod. 69, p2007, 2003; Park, S P. et al. Hum Reprod. 19, p676, 2004; Richards, M. et al. Stem Cells 21, p546, 2003; and Xu, C. et al. Stem Cells 22, p972, 2004), but there has been no report of a successful case with iPS cells.
Further, it is difficult to completely remove feeder cells from iPS cells cultured together with feeder cells. In therapies using iPS cells, it is necessary to reduce the risk of contamination of cells from a different species and other individuals. Thus, a technology to allow usage of cells of the same species or autologous cells in the entire process of establishment and culture of iPS cells is demanded.